The short answer
- Solar panels need little maintenance. They lose a median of about 0.5% of output a year, from NREL's review of nearly 2,000 measurements (NREL).
- Cleaning rarely pays in Southern California: UC San Diego found dirty panels lost less than 0.05% a day, and washing a 5 kW system halfway through a dry summer gained about $20 (UCSD).
- Exceptions: bird droppings, nearly flat panels, and homes downwind of highways, farms or factories.
- The most useful habit is checking your monitoring app monthly for a sudden drop.
What to check
- Monitoring: compare each month with the same month last year; a drop of more than 10–15% on a sunny month deserves a call.
- Inverter: string inverters often need replacing during a system's life; the CPUC cites $1,000 to $2,500 (CPUC). Microinverters and batteries have their own warranties.
- Shade: trees grow; trimming can matter more than cleaning.
- Critters: pigeons nesting under panels are common; mesh guards keep them out.
Cleaning safely
If you clean, rinse with a hose from the ground early or late in the day when panels are cool; avoid pressure washers, harsh cleaners and climbing on the roof. Rain does most of the work in winter.
Warranties
Panel warranties commonly run 25 years for power output (for example Qcells guarantees at least 90.58% at 25 years). If your installer has closed, see orphaned systems.
Checked against official sources on Oct 1, 2026. Sources are linked in the text. Not legal, tax or financial advice.